The effects of exercise and physical activity participation on bone mass and geometry in postmenopausal women: a systematic review of pQCT studies

Hamilton CJ, Swan VJ, Jamal SA

CRD summary

This review concluded that exercise appeared to positively influence bone mass and geometry in postmenopausal women. The possibility of publication and language bias and the unknown quality, small sample sizes and less robust study designs of included studies suggest that these conclusions should be interpreted with caution.

Authors' objectives

To assess the effects of exercise on bone mass and geometry in postmenopausal women.

Searching

MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched to November 2008 for published studies. Search terms were reported. References were handsearched.

Study selection

Randomised controlled trials (RCTs), cross-sectional and prospective studies that used peripheral quantitative computed tomography (pQCT) alone or with other imaging techniques to assess the effects of exercise training or physical activity on bone mass and geometry in postmenopausal women. The outcomes of interest were bone mass and geometry findings by pQCT and dual energy X-ray absorptiometry (DXA) where available.

Most of the studies included postmenopausal women between the ages of 50 and 71 years. The women were Asian, European and North American. Where reported, time since menopause ranged from less than 10 years to 29 years. Mean body mass index (BMI) was less than 30kg/m2 in all included studies. Exercise programmes varied in frequency (from two to five times/week), duration (50 to 100 minutes), training period (six to 12 months) and type of exercise (included high-impact bone loading exercise, low-impact weight bearing exercise, resistance training, balance and agility exercises). The lower limbs were targeted in most of the programmes. All of the participants had no prior history of exercise. Bone mass and geometry measures were made using a variety of machines and tibia and/or radius was assessed.

Two reviewers independently selected studies for inclusion. Disagreements were resolved by discussion.

Assessment of study quality

The authors did not state that they assessed study quality; validity of the statistical methods used was discussed.

Data extraction

Mean differences (%) between groups were calculated where possible. The number of reviewers who extracted data was not reported.

Methods of synthesis

The studies were synthesised narratively.

Results of the review

Twelve studies were included in the review (n=2,224, range 31 to 239): four RCTs (n=671), one non-RCT (n=234), three cross-sectional studies (n=785) and four prospective studies (n=534).

Four RCTs and one non-randomised trial reported site-specific benefits of exercise training on bone mass and geometry. The three cross-sectional studies and three of the four prospective studies reported that exercise was associated with positive effects on bone mass and geometry.

Authors' conclusions

Exercise appeared to positively influence bone mass and geometry in postmenopausal women. The effects were modest and appeared to be dependent on continued participation in exercise and the ability to maintain sufficient exercise intensity.

CRD commentary

The research question was supported by defined inclusion criteria. There were no reported attempts to search unpublished literature and it is unclear whether all languages were searched, so there was a risk of publication and language biases. Study quality was not formally assessed, so the reliability of the results of the studies could not be ascertained. Most of the studies were of less robust study designs. Sample sizes were generally small. Studies were selected by two reviewers, which reduced the risk of error and bias; it was not reported whether such measures were used during data extraction. The diversity of included studies in terms of participants, interventions and study designs suggested that narrative synthesis was appropriate. The authors reported that the results cannot be generalised to all women (as the included studies were of only a few nationalities).

The possibility of publication and language bias and unknown quality, small sample sizes and less robust study designs of the included studies suggests that the authors' conclusions should be interpreted with caution.

Implications of the review for practice and research

Practice: The authors stated that using pQCT as well as DXA may provide a more complete picture of the effects of exercise on bone in postmenopausal women.

Research: The authors stated that more research was needed to understand the types and amounts of exercise necessary to achieve improvements in bone mass and geometry and whether such adaptations were capable of preventing fractures.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.